Fluorescence studies on the conjugated polyelectrolyte DPS-PPV [poly (2,5-dipropoxy sulphonato para phenylene) vinylene] in aqueous solution

The optical properties of various conjugated, water-soluble polymers in general, and MPS-PPV [poly (2-methoxy 5-sulfopropoxy) 1,4-phenylene vinylene] in particular, have been found to be useful in the fabrication of sensors for ionic species. We report our investigations on the influence of various ionic species on the fluorescence properties of DPS-PPV, possessing two sulphonate groups per repeating unit. The emission quantum yield of this polymer exceeds that of the mono-sulphonated derivative by a factor of 10, potentially increasing the sensitivity of such sensors. The fluorescence intensity of aqueous DPS-PPV decreases following the addition of certain cations, and some small spectral shifts occur. The origin of these changes will be discussed based on steady state measurements and excited state dynamics. The emission behavior of DPS-PPV adsorbed onto single silica micro spheres is also reported.